Alcohols have a variety of industrial and scientific applications such as fuels, reagents, and solvents. For example, butanol is an important industrial chemical and drop-in fuel component with a variety of applications including use as a renewable fuel additive, a feedstock chemical in the plastics industry, and a food-grade extractant in the food and flavor industry. Accordingly, there is a high demand for alcohols such as butanol as well as for efficient and environmentally-friendly production methods including, for example, fermentation processes and the use of biomass as feedstock for these processes.
Biomass may be derived from a variety of biological materials such as plants (e.g., corn and sugar cane crops), and cellulosic and lignocellulosic sources. For some production processes such as fermentation, biomass may be treated to generate a fermentable carbon source (e.g., sugars), oil, and undissolved solids which may be added directly to a fermentor. However, the undissolved solids and oil may interfere with the recovery of the fermentative products. For example, the presence of undissolved solids and oil in the fermentation broth may decrease the mass transfer coefficient of a recovery method such as liquid-liquid extraction. In addition, for a method such as liquid-liquid extraction, the presence of the undissolved solids and oil may impede phase separation, may result in the accumulation of oil in the extractant leading to reduced extraction efficiency, may slow the disengagement of extractant droplets from the fermentation broth, and may increase the loss of extractant due to trapping in the undissolved solids.
In addition, removal of oil may also provide beneficial effects on the production of fermentative products as well as commercial benefits. For example, some oils such as corn oil and soybean oil may be used as a feedstock for biodiesel and thus, provide an additional revenue stream for alcohol producers. In addition, removing oil can result in energy savings for the production facility due to more efficient fermentation, decreased equipment fouling, and decreased energy requirements, for example, the energy needed to dry distillers grains.
Thus, there is a continuing need to develop more efficient processes and systems for producing fermentative products such as product alcohols (e.g., ethanol, butanol) using fermentation processes. The present invention satisfies this need and provides processes and systems for producing product alcohols by separating feed stream components prior to the fermentation process and therefore, controlling the amount of undissolved solids and/or oil entering the fermentation process.